Band-gap discontinuities for Ge/ZnSe(100) and Si/ZnSe(100): A photoemission study

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Abstract
Ultraviolet- and x-ray-photoemission and low-energy electron-diffraction studies during room-temperature growth of Ge/ZnSe(100) and Si/ZnSe(100) heterojunctions show that these interfaces are abrupt but disordered. Heterojunction valence-band discontinuities were found to be 1.65±0.1 and 1.55±0.1 eV for Ge/ZnSe and Si/ZnSe, respectively, as determined from the valence-band maxima for ZnSe(100) and the growing overlayers of Ge or Si, with corrections made for band bending. Complementary calculations of the difference in core-level binding-energy positions for the substrate and the overlayer confirmed these results. The final Fermi-level-pinning positions were 1.75±0.1 and 1.85±0.1 eV above the valence-band maximum of ZnSe.